Can one install two copies of firefox on the same computer?

I would like to have two copies of firefox installed on one Windows computer.
They are in two different languages, one in English and one in Japanese.
Is it possible?

Alternatively Japanese with one Window user account and English in all other user accounts on the same computer.
Is it possible too?

I would like to have two copies of firefox installed on one Windows computer.
They are in two different languages, one in English and one in Japanese.
Is it possible?
Alternatively Japanese with one Window user account and English in all other user accounts on the same computer.
Is it possible too?

As stated above, each Firefox must be placed in its own folder.
Also, each must have its own profile.

You can use sync to share the profile data, BUT
different versions may not be able to share certain settings, add-ons . . . .
So sync only passwords and bookmarks.

Download the full installers for each version you want to use.
When you run the installer, select the Manual option
and place each in its own programs folder (see pictures).

Note: Whatever version is loaded Last will be the default.
Also, create the profiles before you start installing other Firefox's.
+++++++++++++++++++++++++++++++++++++++++++++++
With Windows, each Firefox must have its own batch file program
to send the nessassary information into the browser when started.

Usage: C:\PROGRA~1\MOZILL~1\firefox.exe [ options ... ] [URL]
where options include:
-h or -help Print this message.
-v or -version Print Firefox version.
-P <profile> Start with <profile>.
-migration Start with migration wizard.
-ProfileManager Start with ProfileManager.
-no-remote Do not accept or send remote commands; implies -new-instance.
-new-instance Open new instance, not a new window in running instance.
-UILocale <locale> Start with <locale> resources as UI Locale.
-safe-mode Disables extensions and themes for this session.
-console Start Firefox with a debugging console.
-jsconsole Open the Error console.
-browser Open a browser window.
-new-window <url> Open <url> in a new window.
-new-tab <url> Open <url> in a new tab.
-preferences Open Options dialog.
-search <term> Search <term> with your default search engine.
-setDefaultBrowser Set this app as the default browser.

You need to be careful, but it can be done.
As stated above, each Firefox must be placed in its own folder.
Also, each must have its own profile.
You can use sync to share the profile data, BUT
different versions may not be able to share certain settings, add-ons . . . .
So sync only passwords and bookmarks.
Download the full installers for each version you want to use.
When you run the installer, select the Manual option
and place each in its own programs folder (see pictures).
'''Note: '''Whatever version is loaded Last will be the default.
Also, create the profiles before you start installing other Firefox's.
+++++++++++++++++++++++++++++++++++++++++++++++
With Windows, each Firefox must have its own batch file program
to send the nessassary information into the browser when started.
Here is an example (on one line only);
C:\Program Files (x86)\Mozilla Firefox Current\firefox.exe -no-remote -P Firefox_v_57
https://developer.mozilla.org/en-US/docs/Mozilla/Command_Line_Options
Usage: C:\PROGRA~1\MOZILL~1\firefox.exe [ options ... ] [URL]
where options include:
-h or -help Print this message.
-v or -version Print Firefox version.
-P <profile> Start with <profile>.
-migration Start with migration wizard.
-ProfileManager Start with ProfileManager.
-no-remote Do not accept or send remote commands; implies -new-instance.
-new-instance Open new instance, not a new window in running instance.
-UILocale <locale> Start with <locale> resources as UI Locale.
-safe-mode Disables extensions and themes for this session.
-console Start Firefox with a debugging console.
-jsconsole Open the Error console.
-browser Open a browser window.
-new-window <url> Open <url> in a new window.
-new-tab <url> Open <url> in a new tab.
-preferences Open Options dialog.
-search <term> Search <term> with your default search engine.
-setDefaultBrowser Set this app as the default browser.

You can do a custom install in a different Firefox program folder.
You can install additional language packs in a profile to be able to switch the user interface language.
You can use the -UILocale <locale> command line switch to switch the locale or use the <b>about:config</b> page (intl.locale.requested) like written in the KB article.
*https://support.mozilla.org/en-US/kb/use-firefox-interface-other-languages-language-pack

Question owner

Before I venture to install another Firefox on the same system, Could you please tell me if doing "Choose your preferred language for displaying pages" the same as having an edition in that language.

I can't find intl.locale.requested in about:config. I hesitate to add this preference in as it might mean something else. Please comment!

Before I venture to install another Firefox on the same system, Could you please tell me if doing "Choose your preferred language for displaying pages" the same as having an edition in that language.
I can't find intl.locale.requested in about:config. I hesitate to add this preference in as it might mean something else. Please comment!

HI, you can switch between languages as you asked but the code for that has changed and I have no idea how to do intl from about:config now.
You are correct that cor-el's suggestion is not there so I would not add it.

Please let us know if this solved your issue or if need further assistance.

HI, you can switch between languages as you asked but the code for that has changed and I have no idea how to do intl from about:config now.
You are correct that cor-el's suggestion is not there so I would not add it.
Yes it will be in that preferred language but can change it :
*https://support.mozilla.org/en-US/kb/use-firefox-interface-other-languages-language-pack
Suggest backup :
*https://support.mozilla.org/en-US/kb/back-and-restore-information-firefox-profiles
*https://support.mozilla.org/en-US/kb/export-firefox-bookmarks-to-backup-or-transfer
You can also install more than one Firefox or you can run the Developer Edition in compatibility mode.
*https://www.mozilla.org/en-US/firefox/developer/
See answers going on here today for install more than one version :
*https://support.mozilla.org/en-US/questions/1223137
Please let us know if this solved your issue or if need further assistance.

Question owner

I have managed to install an edition of different language in a different folder.

The first thing I've found the same home page was brought across. I suppose I would have lost all the bookmarks too.

The browser ran for a while then hung with a script. I stopped the script but it still hung. I had to use the task manager to kill it.

Then I can't bring up the Start menu. I've got Google Chrome still running and I'm using Google Chrome to write this.

Perhaps I would have to start all over again.

I have managed to install an edition of different language in a different folder.
The first thing I've found the same home page was brought across. I suppose I would have lost all the bookmarks too.
The browser ran for a while then hung with a script. I stopped the script but it still hung. I had to use the task manager to kill it.
Then I can't bring up the Start menu. I've got Google Chrome still running and I'm using Google Chrome to write this.
Perhaps I would have to start all over again.

The Developer Edition would have been the way to go with no fuss no mess but it also shares your Profile and Bookmarks thus backup.

Also tomorrow would have been better as Firefox 61 will be released.
Expect a update tomorrow. Or go to Help --> About if not alerted.

HI, that is why I put the links up above for you to backup.
It is difficult to do to have 2 separate Profiles in 2 places. That is not what it wants to do.
Copy your Profile out please, can be dissected to find out :
*https://support.mozilla.org/en-US/kb/profiles-where-firefox-stores-user-data
*bookmarks and history are in : places.sqlite
The Developer Edition would have been the way to go with no fuss no mess but it also shares your Profile and Bookmarks thus backup.
Also tomorrow would have been better as Firefox 61 will be released.
Expect a update tomorrow. Or go to Help --> About if not alerted.

logins.json (passwords) and key4.db (58+) or key3.db (57 and older) (decryption key) for Passwords saved in the Password Manager

if you only have key3.db then make sure to remove an existing key4.db

cert9.db (58+) or cert8.db (57 and older) for (intermediate) certificates stored in the Certificate Manager

if you only have cert8.db then make sure to remove an existing cert9.db

persdict.dat for words you added to the spelling checker dictionary

permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)

sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

Hi, it looks like you have 3 profiles there.
0 File(s) 0 bytes will have to open them to see if anything is in there.
This is one created today and maybe be the other one you just installed :
26/06/2018 04:36 PM <DIR> a1ckolv7.default
You will have to figure out what you did on these days :
23/06/2018 28/01/2018
*https://support.mozilla.org/en-US/kb/recovering-important-data-from-an-old-profile
*bookmarks and history: places.sqlite
*bookmark backups: compressed .jsonlz4 JSON backups in the bookmarkbackups folder
*cookies.sqlite for the Cookies
*formhistory.sqlite for saved autocomplete Form Data
*logins.json (passwords) and key4.db (58+) or key3.db (57 and older) (decryption key) for Passwords saved in the Password Manager
*if you only have key3.db then make sure to remove an existing key4.db
*cert9.db (58+) or cert8.db (57 and older) for (intermediate) certificates stored in the Certificate Manager
*if you only have cert8.db then make sure to remove an existing cert9.db
*persdict.dat for words you added to the spelling checker dictionary
*permissions.sqlite for Permissions and possibly content-prefs.sqlite for other website specific data (Site Preferences)
*sessionstore.jsonlz4 for open tabs and pinned tabs (see also the sessionstore-backups folder)

IMO, those 3 Profiles are the same Profile within the same Windows Logon User Account.

The "UNIX date stamps" of -1517114227541 and -1508758163783 would correspond to one Profile that was Refreshed twice. A new 8 character 'hash' or 'slt' is created with each Refresh. default is the tip-off that they're all the same Profile that has been Refreshed.

To answer your question - "Can one install two copies of firefox on the same computer?"

Yes, but it isn't necessary with the manner you explained using separate Windows Logon User Accounts {LUA}. " Japanese with one Window user account and English in all other user accounts on the same computer."

Each LUA will have its own Firefox Profile automatically in its own \users\username\Roaming\ AppData\ folder path within Windows, and since Language Packs are installed in a Profile you would only need the Japanese Language Pack installed in that Firefox Profile when the en-US version of Firefox is installed in Windows.

IMO, those 3 Profiles are the '''same''' Profile within the same Windows Logon User Account.
The "UNIX date stamps" of '''-1517114227541''' and '''-1508758163783''' would correspond to one Profile that was Refreshed twice. ''A new 8 character 'hash' or 'slt' is created with each Refresh. '''default''' is the tip-off that they're all the same Profile that has been Refreshed.''
---------------------
To answer your question - '''"Can one install two copies of firefox on the same computer?"'''
'''Yes''', but it isn't necessary with the manner you explained using separate Windows Logon User Accounts {LUA}. '''''" Japanese with one Window user account and English in all other user accounts on the same computer."'''''
Each LUA will have its own Firefox Profile automatically in its own \users\username\Roaming\ AppData\ folder path within Windows, and since Language Packs are installed in a Profile you would only need the Japanese Language Pack installed in that Firefox Profile when the en-US version of Firefox is installed in Windows.

Question owner

Sorry to have given you so much trouble.

I've just downloaded an English edition version 60.0.2 and installed again, just to put it back to what it was before. I don't know when version 61 will be released. I can't wait while there is problem. When I wanted to download the language pack before, it wouldn't download because the pack was for version 61. That was why I downloaded and installed an edition of the language I would like to have.

Would waiting for the next release be the best and easiest option for me?

Sorry to have given you so much trouble.
I've just downloaded an English edition version 60.0.2 and installed again, just to put it back to what it was before. I don't know when version 61 will be released. I can't wait while there is problem. When I wanted to download the language pack before, it wouldn't download because the pack was for version 61. That was why I downloaded and installed an edition of the language I would like to have.
Would waiting for the next release be the best and easiest option for me?

Question owner

I have downloaded the language pack and added on and I have chosen the appropriate language on the settings.

I have restarted it a few times and still haven't seen any change on the interface.

Certainly if I can switch the language on the fly it would even be better.

I have downloaded the language pack and added on and I have chosen the appropriate language on the settings.
I have restarted it a few times and still haven't seen any change on the interface.
Certainly if I can switch the language on the fly it would even be better.

You can set <b>intl.locale.requested</b> to the language code of an installed language pack to select a language.
*https://support.mozilla.org/en-US/kb/use-firefox-interface-other-languages-language-pack
----
You can create a desktop shortcut with the "-UILocale xx-xx" switch appended to the command line to start Firefox with a specific locale.
Start > Run: firefox.exe -UILocale en-US
*https://developer.mozilla.org/en-US/Command_Line_Options

Question owner

I've added intl.locale.requested into about:config but nothing has changed.

I'd presumed this setting refers to where one resides so that the browser bring up the local contents. I just want to use the language but I don't reside there. Does one still need to set this value?

I've added intl.locale.requested into about:config but nothing has changed.
I'd presumed this setting refers to where one resides so that the browser bring up the local contents. I just want to use the language but I don't reside there. Does one still need to set this value?